Replace systemctl --user with podman system service for socket activation

systemctl --user fails in non-interactive shells (no D-Bus session bus).
podman system service starts the socket directly without systemd/D-Bus,
backgrounding the process and waiting up to 5 s for the socket to appear.

https://claude.ai/code/session_01FKCW3FDjNFj6jve4niMFXH

infra/start.sh

@@ -60,13 +60,22 @@ EOF
 echo "[hiy] Generated proxy/caddy.json for ${DOMAIN_SUFFIX}"
 
 # ── Ensure Podman socket is active ────────────────────────────────────────────
+# systemctl --user requires a D-Bus session (not available in non-interactive
+# shells). Use podman system service directly instead.
 PODMAN_SOCK="/run/user/$(id -u)/podman/podman.sock"
-if [ ! -S "$PODMAN_SOCK" ]; then
-    echo "[hiy] Starting Podman socket…"
-    systemctl --user start podman.socket
-fi
 export PODMAN_SOCK
 export DOCKER_HOST="unix://${PODMAN_SOCK}"
+if [ ! -S "$PODMAN_SOCK" ]; then
+    echo "[hiy] Starting Podman socket via podman system service…"
+    mkdir -p "$(dirname "$PODMAN_SOCK")"
+    podman system service --time=0 "unix://${PODMAN_SOCK}" &
+    # Wait up to 5 s for the socket to appear
+    for i in 1 2 3 4 5; do
+        [ -S "$PODMAN_SOCK" ] && break
+        sleep 1
+    done
+    [ -S "$PODMAN_SOCK" ] || { echo "ERROR: Podman socket did not appear"; exit 1; }
+fi
 
 # ── Build images ───────────────────────────────────────────────────────────────
 make build